Lubricant compositions



. 3,223,634 LUBRICANT COMPOSITIONS David X. Klein, Upper Montclair, N.J., assignor, by

mesne assignments, to Tennec'o Chemicals, Inc, a corporation of Delaware No Drawing. Filed May 28, 1963, Ser. No. 283,693 15 Claims. (Cl. 25242.7)

This invention relates to synthetic ester fluids which are resistant to oxidation at elevated temperatures and more particularly to ester lubricant compositions which are useful as lubricants in jet aircraft engines.

Jet aircraft engines require a lubricant which provides the necessary lubricity to minimize the friction and which meets the other requirements with respect to viscosity, thermal stability, fire point, pour point, and the like. The design of more powerful jet engines has led to an increase in the temperatures under which the lubricant is used. For example, a high temperature lubricant should be stable under oxidative conditions at temperatures above 400 F.

Esters of aliphatic acids and polyols are useful as lubricants at elevated temperatures. However, these esters are not sufliciently stable under oxidative conditions at temperatures in the order of 400 F. over extended periods. Under such conditions the esters sludge badly, build up viscosity, and develop high acidity which causes severe corrosion.

It has been discovered that a lubricant comprising as the base fluid a major proportion of a polyol ester and a minor proportion each of a diaromatic secondary amine and a metal chelate of a salicylimine or S-nitrosalicylimine has excellent stability under oxidative conditions at elevated temperatures.

The polyol esters are esters of a single or a mixture of polyols and a single or a mixture of saturated, straight or branched chain, monocarboxylic aliphatic acids. Alternatively saturated, aliphatic dicarboxylic acids may be used as part of the esterification acids. The anhydrides of the monocarboxylic or dicarboxylic acids may be used and are equivalents.

The preferred polyols are the neopentyl alcohols containing from 2 to 4 methylol groups although other alcohols containing from 2 to 4 hydroxyl groups may be used as is known in the prior art. Among the preferred polyols are trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, neopentyl glycol, 2-butyl- 2-ethyl-1,3-propanediol, and 2,2,4-trimethyl-1,3-pentanediol.

The saturated monocarboxylic acids may contain from 2 to 18 carbons depending in part on the polyol but primarily on the viscosity requirements and to a certain extent on whether or not mixtures of acids are used. In general, acids containing 12 or more carbon atoms produce esters which are solids at room temperature although this can be overcome in part by the use of a mixture of such a long'chain acid with a short chain acid. Particularly for base fluids which must also be fluid at room temperature and preferably have a pour point of 40 F. or less, better results are obtained with acids containing from 4 to carbon atoms. The preferred acids are those containing from 5 to 9' carbon atoms with optimum results being obtained with a single acid or a mixture of acids containing an average of from 5 to 8 carbon atoms.

When a dicarboxylic, saturated aliphatic acid is used, the amount used of such acid is one mole of acid per two moles of polyol to produce an ester of the formula, R-acidR, where R represents the alcohol moiety. The remaining hydroxyl groups of the alcohol are esterified with the monocarboxylic acids previously de- United States Patent 0 3,223,634 Patented Dec. 14, 1965 ice scribed. The dibasic acids are saturated aliphatic acids and they may contain from 3 to 36 carbon atoms in their formula. The preferred acids are sebacic acid, azelaic acid, and adipic acid. However, the present invention is not limited to these acids and mixtures of such acids, for

example, a mixture of sebacic and adipic acids, may be" used. Illustrative esters are disclosed in United States Patent No. 3,048,608 and British Patent No. 915,161, published January 9, 1963.

The following esters are illustrative of those which may be used as the base fluid; however, it is to be understood that these are not the only esters which may be used: trimethylolpropane divalerate monopelargonate, tri methylolpropane monovalerate monocapro ate monocaprylate, trimethylolpropane divalerate monoheptanoate, trimethylolpropane dibutyrate monopelargonate, trimethylolethane divalerate monopelargonate, trimethylolethane dicaproate monocaprylate, trimethylolethane dibutyrate monopelargonate, bis (neopentyl glycol monopelargonate) azelate, bis (pentaerythritol trivalerate) adipate, bis (pentaerythritol tricaproate) sebacate, pentaerythritol tetracaproate, and pentaerythritol dicaproate divalerate.

The preparation of such esters is known and any suitable procedure may be followed. Preferably the polyol esters are prepared by the esterification of the polyol in the presence of a slight excess of the monocarboxylic acid to promate the production of esters substantially free of hydroxyl groups. If a dicarboxylic acid is used, it is used in an amount equal to one mole of acid per two moles of polyol, and the dicarboxylic: acid may be reacted with the polyol prior to or at the same time as the monocarboxylic acid. The esterification may be carried out, for example, at temperatures in the range of about 240 C. Water is removed preferably but not necessarily in the presence of an azeotropic agent such as a liquid hydrocarbon. Any unreacted acid should be removed. The preparation of such esters is disclosed in United States 'Patent No. 3,036,005 and in the A05. Monograph No. 136 (The Pentaerythritols; Berlow, Barth, and Snow; 1958).

The diaromatic secondary amines include diaryl amines, aryl-alkaryl amines and dialkaryl amines, with the aryl groups preferably having no more than 5 benzene rings and the alkyl substituents, when present, having no more than 24 carbon atoms. Among the specific diaromatic secondary amines which may be used are phenyl-anaphthylamine, p,pdioctyldiphenylamine, and phenyl-finaphthylamine.

The metal chelates may be prepared from 'salicylaldehyde or S-nitro-salicylaldehyde, an amine and the metal as the chloride, in the manner described in Shrine and Fuson, Systematic Identification of Organic Compounds, 4th edition, page 112. The reactions involved may be represented by the following equation:

wherein Y represents N or H; M represents Ni, Co, or Zn; and R represents C Haand X represents H, CH or Cl. Illustrative metal are those prepared from the following materials:

Aldehyde Amine Metal 5-Nitrosalicylaldehyde Aniline 5-Nitrosalicyla1dehyde p-Phenoxy aniline Do. Salicylaldehyde Aniline Do. 5-Nitrosalicylaldehyde Aniline Zinc. 5-Nitrosalieylaldehyde p-Phenoxyphenoxy aniline. Nickel. 5-Nitrosalicylaldehyde o-Toluidine D o. 5-Nitrosalieylaldehyde. o-Ohloroaniline- Do. 5-Nitrosalicylaldehyde. Z-ethylhexylamine D0. E-Nitrosalicylaldehyde Aniline Cobalt are representative of trimethylolpropane divalerate monopelargonate prepared by this procedure.

Acid number 0.028 Hydroxyl content percent 0.08 Saponification value 378.8 Flash point F 435 Pour point F 92 Viscosity (centistokes):

at 210 F. 3.39

at 100 F 14.30

at 65 F. 12,830 Viscosity index (Dean and Davis) 127.4

Example 2 Polyol esters of trimethylolpropane divalerate monopelargonate prepared in the manner described in Example 1 were subjected to oxidation tests with and without various additives. These tests were performed using a 20 m1. portion maintained at 425 F. for 24 hours with 20 liters per hour of dry air flow through the fluid. In each instance the viscosity and acid number were determined prior to the test. After the test the amount of fluid lost was determined as was the viscosity and acid number and the percent change in viscosity at 100 F. was calculated. Each test was run in replicate. The compositions tested were (1) polyol ester base fluid with no additive, (2) polyol ester base fluid containing 1% by weight of phenyla-naphthylamine and 1% by weight of nickel bis (N-phenyl-S-nitrosalicylimine), (3) polyol ester base fluid containing 1% by weight of nickel bis (N-phenyl-S-nitrosalicylimine) alone, and (4) polyol base fluid containing 1% by weight of N-ethylphenodiphenyl silazine. The last mentioned combination is described in U.S. Patent No. 3,036,005. The foregoing percentages of additives are based on the weight of the polyol ester.

TABLE I Before Test After Test Fluid Viscosity Percent Viscosity Percent Remarks 7 (centistokes) Acld Fluid (centistokes) Viscosity Acid at 100 F. Number Loss at 100 F. CharggEe at Number Base fluid, no additive .85 0. 2 33. 2 513. 4 3, 346. 16. 6 Dlaarlkened badly, no insolu- Replicate 14. 85 0. 2 32. 7 460. 9 2, 993. 13.6 Do. Base fluid containing 1% by Weight of 15.50 0.3 3.8 16.59 7.03 0.1 Darkened; negligible insoluphenyL-a-naphthylamine and 1% by bles.

weight of nickel bis (N phenyl-5-nitrosalicylimine). Replicate 15. 0.3 6. 1 16. 70 7. 74 0. 1 Do. Base fluid containing 1% by welght of 15.23 0.2 26.3 343.2 2,153. 14.7 Darkened; moderate insolun1cke)l bis (Nphenyl-5-n1trosalieylible formation.

mine Replicate 15.23 0.2 22.0 185. 5 1, 118. 15.6 Do. Base fluid containing 1% by weight of 15.60 0.3 6.4 17.47 12.0 0.4 Darkened; no insolubles.

phenyl-a-naphthylamine and 1% by vgeight of N-ethyl-phenodiphenyl silaz ne. Replicate 15. 0.3 6. 5 17. 69 13. 4 0. 5 Do.

22.1 grams of activated carbon is heated to 175-180 60 Example 3 neutralize the unreacted acid and then with 12% sodium chloride solution until neutral. After the addition of about 2% by weight of activated carbon, the solution is heated at about 40 C. at about 20 mm.. absolute pressure and then at 160-180 C. at 2 mm. absolute pressure to remove the water, petroleum ether, and any other low boiling materials that may be present. The residue is cooled to 100 C. and filtered. The following properties The ester base fluid of Example 1 containing additives was subjected to wear tests in a precision-Shell four b all extreme pressure tester. This test is described in the literature. Briefly stated, the tester comprises a holder for holding three lower balls in fixed positions. An upper ball is pressed against the lower fixed balls under a predetermined load and rotated while the three points of contact are lubricated with the lubricant under test. The diameters of the three load scars on the lower balls are: measured. In this example two lubricants were subjected to comparative tests. In one series of tests, theupper ball was rotated at 1200 r.p.m. for two hours at 167 F. In a second series of tests, the upper ball was rotated at 600 r.p.m. for two hours at 400 F. In each series of tests two somewhat different groups of balls were used. One group was of mild steel and the other group was of stainless steel. The loads applied were kilograms and 40 kilograms, respectively. At the end of each test the diameter of the scar on each of the three lower balls was measured both vertically and horizontally and the average of the six measurements in millimeters is the value used for the scar diameter in describing the results.

Lubricant composition A was the base fluid containing 1% by weight of phenyl-a-naphthylamine and 1% by weight of N-ethylphenodiphenyl silazine. The second composition, composition B, was the base fluid containing 1% by weight of phenyl-a-naphthylamine and 0.8% by weight of nickel bis (N-phenyl-S-nitrosalicylimine). In preparing composition B, 1% of the chelate was added. The composition was filtered and undissolved chelate removed, leaving 0.8% chelate in the lubricant.

TABLE II 600 r.p.m., 2 hours, 400 F.

Fluid Mild Stainless Steel Balls Steel Balls 10 Kg. 40 Kg. 10 Kg. 40 Kg.

Composition A:

Scar diameter 0. 742 1.068 0. 454 1 0.835 Oil change Composition B:

Scar diameter 0. 371 0. 884 0. 475 0.683 Oil change 1200 r.p.m., 2 hours, 167 F.

Mild Stainless Fluid Steel Balls Steel Balls 10 Kg. 40 Kg. 10 Kg. 40 Kg.

Composition A:

Scar diameter .t 0.681 0. 864 0. 444 0. 876 Oil change Composition B:

Scar diameter 0. 510 0.787 0. 508 1 0. 824 Oil change NOTE:

1 Wear scar is rough.

2 Oil darkened.

3 No change in oil color.

Scar diameter=Average of six measurements.

The present combination of additives in lubricant B compares favorably with the previously known combination of additives in lubricant A. This known combination is one of the best antioxidants available up to this time for high temperature synthetic ester lubricants and was used for comparative purposes for this reason.

The diaromatic secondary amine :and the metal chelate each will be used normally in an amount in the range of fron 0.25% to 3% by weight of the polyol ester and preferably in an amount in the range of from 0.5% to 2% by weight of the polyol ester. However, the present invention is not limited to these amounts and larger amounts may be used although such larger amounts will be a minor amount based on the weight of the polyol esters. These two materials may be added separately to the polyol ester or may be pre-mixed for subsequent use.

A mixture of metal chelates may be used and may be preferred as, in general, the ohelates prepared from salicylaldehyde increase the solubility of the chelates prepared from S-nitro-salicylaldehyde. Mixtures of these two aldehydes may be used in preparing the chelates. Also, a mixture of amines, for example, a mixture of aniline and p-phenoxyaniline, may be used in preparing the chelates.

The lubricant compositions also may contain other ad ditives such as detergents, pour point depressants, viscosity index improvers, etc. The base fluid need not 6 consist of the polyol ester and may include other lubricants.

I claim: 1. A lubricant composition comprising an aliphatic acid ester of a polyol containing from 2 to 4 hydroxyl H R R H Iii:

wherein Y represents a member selected from the group consisting of N0 and H; M represents a member selected from the group consisting of Ni, Co, and Zn; R represents a member selected from the group consisting of CH -0 H and X represents a member selected from the group consisting of H, CH and Cl.

2. A lubricant composition comprising an acid ester of a neopentyl alcohol containing from 2 to 4 methylol groups, said acid being selected from the group consisting of (l) saturated, aliphatic monocarboxylic acids and (2) at least one saturated, aliphatic monocarboxylic acid and at least one saturated, aliphatic dicarboxylic acid, said ester being stabilized against oxidative degradation by from 0.25% to 3% by weight of a diaromatic secondary amine selected from the group consisting of diaryl amines, aryl alkaryl amines and d-ialkaryl amines, and from 0.25% to 3% by weight of metal chelate represented by the formula:

wherein Y represents a member selected from the group consisting of N0 and H; M represents a member selected from the group consisting of Ni, Co, and Zn; R represents a member selected from the group consisting of 7 and X represents a member selected from the group consisting of H, CH and Cl.

3. A lubricant composition comprising an acid ester of a neopentyl alcohol containing from 2 to 4 methylol groups, said acid being saturated, aliphatic monocarboXylic acid containing from 4 to 10 carbon atoms, said ester being stabilized against oxidative degradation by a minor amount based on the amount of ester of a diaromatic secondary amine selected from the group consisting of diaryl amines, aryl alkaryl amines and dialkaryl amines, and a minor amount based on the amount of ester of metal chelate represented by the formula:

wherein Y represents a member selected from the group consisting of N and H; M represents a member selected from the group consisting of Ni, Co, and Zn; R represents a member selected from the group consisting of and and X represents a member selected from the group consisting of H, CH and Cl.

4. A lubricant comprising a major proportion of an acid ester of a neopentyl alcohol containing from 2 to 4 methylol groups, said acid being a mixture of saturated, aliphatic monocarboxylic acids containing an average of from 5 to 8 carbon atoms, said ester being stabilized against oxidative degradation by a minor amount based on the amount of ester of a diar'omatic secondary amine selected from the group consisting of diaryl amines, aryl alkaryl amines and dialkaryl amines, and a minor amount based on the amount of ester of metal chelate represented by the formula:

wherein Y represents a member selected from the group consisting of N0 and H; M represents a member selected from the group consisting of Ni, Co, and Zn; R represents a member selected from the group consisting of Oil and

C 113-? C H.

and X represents a member selected from the group consisting of H, CH and Cl.

5. A lubricant comprising a major proportion of an aliphatic acid ester of a polyol containing from 2 to 4 hydroxyl groups, said acid being selected from the group consisting of (l) saturated, aliphatic monocarboxylic acids, and (2) at least one saturated, aliphatic monocarboxylic acid and at least one saturated, aliphatic dicarboxylic acid, said ester being stabilized against oxidative degradation by a minor amount based on the amount of ester of phenyl-a-naphthylamine, and a minor amount based on the amount of ester of nickel bis (N-phenyl-S- nitrosalicylimine 6. A lubricant comprising a major proportion of an acid ester of a neopentyl alcohol containing from 2 to 4 methylol groups, said acid being saturated, aliphatic monocarboxylic acid containing from 4 to 10 carbon atoms, said ester being stabilized against oxidative degradation by a minor amount based on the amount of ester of phenyl-a-naphthylamine, and a minor amount based on the amount of ester of nickel bis (N-phenyl-S-nitrosalicylimine) 7. A lubricant comprising a major proportion of an acid ester of trimethylolethane, said acid being saturated, aliphatic monocarboxylic acid containing from 4 to 10 carbon atoms, said ester being stabilized against oxidative degradation by a minor amount based on the amount of ester of phenyl-a-naphthylamine, and a minor amount based on the amount of ester of nickel bis (N-phenyl-S- nitrosalicylimine) 8. A lubricant comprising a major proportion of an acid ester of trimethylolpropane, said acid being satu rated, aliphatic monocarboxylic acid containing from 4 to 10 carbon atoms, said ester being stabilized against oxidative degradation by from 0.25% to 3% by Weight of phenyl-ot-naphthylamine, and from 0.25% to 3% by weight of nickel bis (N-phenyl-S-nitrosalicylimine).

9. A lubricant comprising a major proportion of an acid ester of pentaerythritol, said acid being saturated, aliphatic monocarboxylic acid containing from 4 to 10 carbon atoms, said ester being stabilized against oxidative degradation by from 0.25% to 3% by weight of phenyl-rx-naphthylamine, and from 0.25% to 3% by weight of nickel bis (N-phenyl-S-nitrosalicylmine).

10. A lubricant composition comprising trimethylolpropane divalerate monopelargonate and from 0.25% to 3% by weight of phenyl-a-naphthylamine, and from 0.25 to 3% by weight of nickel bis( N-phenyl-S-nitrosalicylimine) r 11. An anti-oxidant composition comprising a dimejmatic secondary amine selected from the group consisting of diaryl amines, aryl-alkaryl amines and dialkaryl amines, and a metal chelate represented by the formula:

wherein Y represents a member selected from the group consisting of N0 and H; M represents a member selected from the group consisting of Ni, Co, and Zn; R represents a member selected from the group consisting of and and X represents a member selected from the group consisting of H, CH and C1, the said components being present in a. weight ratio of from 0,25 :3 to 3: 25.

12. An anti-oxidant composition comprising phenyl-anaphthylamine and a metal chelate represented by the formula:

wherein Y represents a member selected from the group consisting of N0 and H; M represents a member selected from the group consisting of Ni, Co, and Zn; R

represents a member selected from the group consisting of 15 10 and X represents a member selected from the group consisting of H, CH and C1, the said components being present in a Weight ratio of from 0.25:3 to 3:025.

13. An anti-oxidant composition comprising phenyl-anaphthylamine and nickel bis (N-phenyl-5-nitrosalicylimine) in a weight ratio of from 0.25:3 to 310.25.

14. An anti-oxidant composition comprising phenyl-anaphthylamine and nickel bis (N-phenyl-5-nitrosy1acylimine) in a weight ratio of from 0.5:2 to 2:05.

15 An anti-oxidant composition comprising phenyl-anaphthylamine and nickel bis (N-phenyl-S-nitrosalicylimine) in equal amounts by Weight.

References Cited by the Examiner UNITED STATES PATENTS 10/1952 Burgess 260429 5/1962 Koch 25249.6

OTHER REFERENCES 5 DANIEL E. WYMAN, Primary Examiner. 

1. A LUBRICANT COMPOSITION COMPRISING AN ALIPHATIC ACID ESTER OF A POLYOL CONTAINING FROM 2 TO 4 HYDROXYL GROUPS, SAID ACID BEING SELECTED FROM THE GROUP CONSISTING OF (1) SATURATED, ALIPHATIC MONOCARBOXYLIC ACIDS AND (2) AT LEAST ONE SATURATED, ALIPHATIC MONOCARBOXYLIC ACID AND AT LEAST ONE SATURATED, ALIPHATIC DICARBOXYLIC ACID, SAID ESTER BEING STABILIZED AGAINST OXIDATIVE DEGRATION BY A MINOR AMOUNT RELATIVE THE AMOUNT OF ESTER OF A DAROMATIC SECONDARY AMINE SELECTED FROM THE GROUP CONSISTING OF DIARYL AMINES, ARYL ALKARYL AMINES AND DIAKARYL AMINES, AND A MINOR AMOUNT RELATIVE THE AMOUNT OF ESTER OF METAL CHELATE REPRESENTED BY THE FORMULA: 